Illumination device and projector with fluorescent plate

ABSTRACT

An illumination device includes: a light source device adapted to emit an excitation light beam; and a rotating fluorescent plate having a single fluorescent layer adapted to convert a part or whole of the excitation light beam into a fluorescent light beam. The fluorescent light beam includes two or more colored light beams, and the single fluorescent layer is formed on a circular disk, which can be rotated by a motor, continuously along a circumferential direction of the circular disk.

BACKGROUND

1. Technical Field

The present invention relates to an illumination device and a projector.

2. Related Art

In the past, as an illumination device used for a projector, there hasbeen known an illumination device having a light source device foremitting the excitation light (blue light), and a rotating fluorescentplate obtained by providing three segment areas to a circular disk,which can be rotated by an electric motor, and is provided with twotypes of fluorescent layers emitting light beams with respective colorsdifferent from each other (a red light beam and a green light beam)respectively in the two segment areas thereof (see, e.g.,JP-A-2009-277516). It should be noted that the remaining segment areaout of the three segment areas provided with no fluorescent layer isprovided with a scattering layer for scattering the excitation light(the blue light) at a predetermined scattering intensity.

According to the illumination device of the related art, it becomespossible to obtain a plurality of colored light beams (the red lightbeam, the green light beam, and the blue light beam) using the lightsource device for emitting the excitation light.

However, in the illumination device of the related art, since the twotypes of fluorescent layers need to be formed on the circular disk,there arises a problem that the manufacturing process of the rotatingfluorescent plate becomes complicated.

Further, in the illumination device of the related art, since the typesof the colored light beams emitted from the illumination device aresequentially switched at high rate in accordance with the rotation ofthe rotating fluorescent plate, there exists a problem that it isdifficult to apply the illumination device to the liquid crystalprojector “of a non-color sequential type having a strong characteristicof being capable of projecting a gentle image with no color breakupphenomenon and being capable of performing fine gradation expression tothereby be capable of projecting a natural image.”

SUMMARY

An advantage of the invention is to provide an illumination device,which can obtain a plurality of colored light beams using the lightsource device for emitting the excitation light, can make themanufacturing process of the rotating fluorescent plate relativelysimple, and can be applied to a liquid crystal projector. Further, theinvention has an advantage of providing a projector equipped with suchan illumination device.

1. According to an aspect of the invention, there is provided anillumination device including a light source device adapted to emit anexcitation light beam, and a rotating fluorescent plate having a singlefluorescent layer formed on a circular disk, which can be rotated by amotor, continuously along a circumferential direction of the circulardisk. The single fluorescent layer converts a part or whole of theexcitation light beam into a fluorescent light beam that includes two ormore colored light beams.

Therefore, according to the illumination device of this aspect of theinvention, since there are provided the light source device for emittingthe excitation light and the rotating fluorescent plate provided withthe fluorescent layer for converting a part or the whole of theexcitation light into the fluorescent light that includes two or morecolored light beams, it becomes possible to obtain the a plurality ofcolored light beams using the light source for emitting the excitationlight.

Further, according to the illumination device of this aspect of theinvention, since the rotating fluorescent plate provided with a singlefluorescent layer is used, it becomes possible to make the manufacturingprocess of the rotating fluorescent plate relatively simple.

Further, according to the illumination device of this aspect of theinvention, since there is used the rotating fluorescent plate having thesingle fluorescent layer formed continuously along the circumferencedirection of the circular plate, it results in that the same coloredlight beam is always emitted from the illumination device, and as aresult, it becomes possible for the illumination device to be applied tothe liquid crystal projector of the non-colorsequential type havingstrong characteristics.

Further, according to the illumination device of this aspect of theinvention, since there is provided the rotating fluorescent plateobtained by providing the single fluorescent layer to the rotatablecircular plate, the heat generated in the fluorescent layer due to theirradiation with the excitation light can be radiated in a large areaalong the circumferential direction, and as a result, it becomespossible to prevent the deterioration of the fluorescent layer anddegradation of the luminous efficiency due to overheat of thefluorescent layer.

2. In the illumination device of the above aspect of the invention, itis preferable that the light source device emits a blue light beam asthe excitation light beam, and the fluorescent layer converts a part ofthe blue light beam emitted from the light source device into thefluorescent light beam that includes a red light beam and a green lightbeam, and transmits a part of a remaining part of the blue light beamwithout performing the conversion.

By adopting such a configuration as described above, it becomes possibleto emit the white light beam from the illumination device using thelight source device for emitting the blue light beam.

3. In the illumination device of the above aspect of the invention, itis preferable that the light source device emits one of a violet lightbeam and an ultraviolet light beam as the excitation light beam, and thefluorescent layer converts the one of the violet light beam and theultraviolet light beam emitted from the light source device into thefluorescent light beam that includes a red light beam, a green lightbeam, and a blue light beam.

By adopting such a configuration as described above, it becomes possibleto emit the white light beam from the illumination device using thelight source device for emitting the violet light beam or theultraviolet light beam.

4. In the illumination device of the above aspect of the invention, itis preferable that the light source device emits a blue light beam asthe excitation light beam, and the fluorescent layer converts the bluelight beam emitted from the light source device into the fluorescentlight beam that includes a red light beam and a green light beam.

By adopting such a configuration as described above, it becomes possibleto emit the light beam including the red light beam and the green lightbeam from the illumination device using the light source device foremitting the blue light beam.

5. In the illumination device of the above aspect of the invention, itis preferable that the circular disk is made of a material transmittingthe excitation light beam, the fluorescent layer is formed on thecircular disk via a dichroic film adapted to transmit the excitationlight beam and to reflect the fluorescent light beam, and the excitationlight beam is arranged to enter the rotating fluorescent plate from aside of the circular disk.

By adopting such a configuration as described above, it becomes possibleto emit the illumination light beam from the illumination device usingthe so-called transmissive rotating fluorescent plate.

6. In the illumination device of the above aspect of the invention, itis preferable that the fluorescent layer is formed on the circular diskvia a reflecting film adapted to reflect a visible light beam, and theexcitation light beam is arranged to enter the rotating fluorescentplate from a side of the fluorescent layer.

By adopting such a configuration as described above, it becomes possibleto emit the illumination light beam from the illumination device usingthe so-called reflective rotating fluorescent plate.

7. In the illumination device of the above aspect of the invention, itis preferable that a light collection optical system disposed in a lightpath from the light source device to the rotating fluorescent plate, andadapted to make the excitation light beam enter the fluorescent layer ina roughly focused state is further provided.

By adopting such a configuration, it becomes possible to emit thefluorescent light in a small area, and as a result, it becomes possibleto improve the light efficiency.

It should be noted that it is preferable that the light collectionoptical system makes the excitation light beam enter the fluorescentlayer so as to fit the square 5 mm on a side, preferably 1 mm on a side.

8. In the illumination device of the above aspect of the invention, itis preferable that the rotating fluorescent plate rotates at arotational speed at which a focused spot of the excitation light beammoves on the fluorescent layer at a predetermined relative speed in arange of 5 m/sec through 50 m/sec.

By adopting such a configuration, since the focused spot of theexcitation light beam moves on the fluorescent layer at sufficientlyhigh relative speed, it becomes possible to reduce the temperature risecaused in the fluorescent layer due to the irradiation with theexcitation light to extremely low level, and as a result, it becomespossible to better prevent the deterioration of the fluorescent layerand the degradation of the luminous efficiency due to the overheat ofthe fluorescent layer. It should be noted that it becomes difficult tosufficiently reduce the temperature rise in the fluorescent layer at therotational speed lower than 5 m/sec. Further, the rotational speedhigher than 50 m/sec increases the noise and the load of the electricmotor.

It should be noted that it is preferable that the rotating fluorescentplate rotates at a rotational speed at which a focused spot of theexcitation light beam moves on the fluorescent layer at a predeterminedrelative speed in a range of 9 m/sec through 35 m/sec.

9. In the illumination device of the above aspect of the invention, itis preferable that the light source device is formed of a laser source.

By adopting such a configuration, since the laser source capable ofinstantaneous lighting is used as the light source, it becomes possibleto project the projection image immediately after powering on.

Further, since the laser source with high light collecting power is usedas the light source, it becomes possible to emit the fluorescent lightin a smaller area, and as a result, it becomes possible to betterimprove the light efficiently.

10. According to another aspect of the invention, there is provided aprojector including the illumination device according to one of theabove aspect of the invention, a light modulation device adapted tomodulate an illumination light beam emitted from the illumination devicein accordance with image information, and a projection optical systemadapted to project the modulated light emitted from the light modulationdevice as a projection image.

Therefore, according to the projector of this aspect of the invention,it becomes possible to provide a projector, which can obtain a pluralityof colored light beams using the light source device for emitting theexcitation light, can make the manufacturing process of the rotatingfluorescent plate relatively simple, and can be realized as a liquidcrystal projector.

11. In the projector of the above aspect of the invention, it ispreferable that the light source device emits a blue light beam as theexcitation light beam, and the fluorescent layer converts a part of theblue light beam emitted from the light source device into thefluorescent light beam that includes a red light beam and a green lightbeam, and transmits a part of a remaining part of the blue light beamwithout performing the conversion.

By adopting such a configuration as described above, it becomes possibleto project a full-color image using the light source device for emittingthe blue light beam.

12. In the projector of the above aspect of the invention, it ispreferable that the light source device emits one of a violet light beamand an ultraviolet light beam as the excitation light beam, and thefluorescent layer converts the one of the violet light beam and theultraviolet light beam emitted from the light source device into thefluorescent light beam that includes a red light beam, a green lightbeam, and a blue light beam.

By adopting such a configuration as described above, it becomes possibleto project a full-color image using the light source device for emittingthe violet light beam or the ultraviolet light beam.

13. In the projector of the above aspect of the invention, it ispreferable that a second illumination device adapted to emit a bluelight beam is further provided, the light source device emits a bluelight beam as the excitation light beam, and the fluorescent layerconverts the blue light beam emitted from the light source device intothe fluorescent light beam that includes a red light beam and a greenlight beam.

By adopting such a configuration, it becomes possible to project thefull-color image using the illumination device for emitting the redlight beam and the green light beam and the second illumination devicefor emitting the blue light beam.

14. In the projector of the above aspect of the invention, it ispreferable that a colored light beam combining element adapted tocombine the blue light beam emitted from the second illumination deviceand the red light beam and the green light beam emitted from therotating fluorescent plate with each other.

By adopting such a configuration, it becomes possible to standardize theoptical system of the illumination device and the optical system of thesecond illumination device to some extent to thereby better simplify theconfiguration of the projector.

15. In the projector of the above aspect of the invention, it ispreferable that the second illumination device includes a second lightsource device adapted to emit the blue light beam, and a scatteringplate adapted to scatter the light beam emitted from the second lightsource device at a predetermined scattering intensity.

By adopting such a configuration as described above, it becomes possibleto uniform the light distributions of the red light and the green lightemitted from the illumination device and the light distribution of theblue light emitted from the second illumination device with each otherto thereby project a more high-quality projection image.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a top view showing an optical system of a projector accordingto a first embodiment of the invention.

FIGS. 2A and 2B are graphs showing the emission characteristics of alight source device and a fluorescent layer in the first embodiment.

FIGS. 3A and 3B are diagrams for explaining a rotating fluorescent platein the first embodiment.

FIG. 4 is a top view showing an optical system of a projector accordingto a second embodiment of the invention.

FIG. 5 is a graph showing the emission characteristics of a second lightsource device in the second embodiment.

FIG. 6 is a top view showing an optical system of a projector accordingto a third embodiment of the invention.

FIGS. 7A and 7B are diagrams for explaining a rotating fluorescent platein the third embodiment.

FIG. 8 is a top view showing an optical system of a projector accordingto a fourth embodiment of the invention.

FIG. 9 is a top view showing an optical system of a projector accordingto a fifth embodiment of the invention.

FIGS. 10A through 10D are graphs showing the emission characteristics ofa light source device and a fluorescent layer in the fifth embodiment.

FIGS. 11A and 11B are diagrams for explaining a rotating fluorescentplate in a modified example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, illumination devices and projectors according to theinvention will be explained based on some embodiments illustrated in theaccompanying drawings.

First Embodiment

FIG. 1 is a top view showing an optical system of a projector 1000according to a first embodiment of the invention. It should be notedthat in FIG. 1, in order for making the explanation easy, theconstituents of the rotating fluorescent plate 30 are illustrated withthe thickness thereof exaggerated. The same can be applied to thedrawings mentioned later.

FIGS. 2A and 2B are graphs showing the emission characteristics of alight source device 10 and a fluorescent layer 42 in the firstembodiment. FIG. 2A is a graph showing the emission characteristics ofthe light source device 10, and FIG. 2B is a graph showing the emissioncharacteristics of the fluorescent layer 42. The emissioncharacteristics denotes the characteristics of the light source deviceregarding the wavelength and the intensity of the light emittedtherefrom in response to application of the voltage, or thecharacteristics of the fluorescent material regarding the wavelength andthe intensity of the light emitted therefrom in response to input of theexcitation light. The vertical axes of the graphs represent the relativeemission intensity assuming that the emission intensity at thewavelength at which the emission intensity is the highest is 1. Thelateral axes of the graphs represent the wavelength.

FIGS. 3A and 3B are diagrams for explaining the rotating fluorescentplate 30 in the first embodiment. FIG. 3A is a front view of therotating fluorescent plate 30, and FIG. 3B is a cross-sectional viewalong the line A1-A1 shown in FIG. 3A.

Firstly, the configuration of the illumination device 100 and theprojector 1000 according to the first embodiment will be explained.

As shown in FIG. 1, the projector 1000 according to the first embodimentis provided with the illumination device 100, a color separation lightguide optical system 200, three liquid crystal light modulation devices400R, 400G, and 400B as a light modulation device, a cross dichroicprism 500, and the projection optical system 600.

The illumination device 100 is provided with a solid-state light sourcedevice 10, a light collection optical system 20, the rotatingfluorescent plate 30, an electric motor 50, a collimating optical system60, a first lens array 120, a second lens array 130, a polarizationconversion element 140, and an overlapping lens 150.

The light source device 10 is composed of a laser source for emitting ablue light beam (having a peak emission intensity at a wavelength of 445nm, see FIG. 2A), which is a laser beam, as the excitation light beam.What is denoted with the symbol B in FIG. 2A is a colored lightcomponent emitted by the light source device 10 as the excitation lightbeam (the blue light beam). It should be noted that the light sourcedevice can be composed of a single laser source or a plurality of lasersources. Further, it is also possible to adopt a light source foremitting a blue light beam having a wavelength (e.g., 460 nm) other than445 nm.

The light collection optical system 20 is provided with a first lens 22and a second lens 24. The light collection optical system 20 is disposedin the light path from the light source device 10 to the rotatingfluorescent plate 30, and collectively makes the blue light beam enterthe fluorescent layer 42 (described later) in a roughly collectedfocused state. The first lens 22 and the second lens 24 are each formedof a convex lens.

The rotating fluorescent plate 30 is of a so-called transmissive type,and is obtained by continuously forming a single fluorescent layer 42 ona part of a circular disk 40 along the circumferential direction of thecircular disk 40 as shown in FIGS. 1, 3A, and 3B. The circular disk 40can be rotated by the electric motor 50. The area where the fluorescentlayer 42 is formed includes an area where the blue light beam enters.The rotating fluorescent plate 30 is configured so as to emit the redlight beam and the green light beam toward the side opposite to the sideto which the blue light beam is input.

The rotating fluorescent plate 30 rotates 7,500 rpm in use. Although thedetailed explanation will be omitted, the rotating fluorescent plate 30has a diameter of 50 mm, and is configured so that the light axis of theblue light beam entering the rotating fluorescent plate 30 is located atthe position approximately 22.5 mm distant from the rotational center ofthe rotating fluorescent plate 30. In other words, the rotatingfluorescent plate 30 rotates at a rotational speed at which the focusedspot of the blue light beam moves on the fluorescent layer 42 at 18m/sec.

The circular disk 40 is made of a material transmitting the blue lightbeam. As the material of the circular disk 40, there can be used quartzglass, quartz crystal, sapphire, optical glass, transparent resin, andso on.

It is arranged that the blue light beam emitted from the light sourcedevice 10 enters the rotating fluorescent plate 30 from the side of thecircular disk 40.

The fluorescent layer 42 is formed on the circular disk 40 via adichroic film 44 that transmits the blue light beam and reflecting thered light beam and the green light beam. The dichroic film 44 is formedof, for example, a dielectric multilayer film.

The fluorescent layer 42 converts a part of the blue light beam emittedfrom the light source device 10 into the fluorescent light beam thatincludes the red light and the green light, and at the same timetransmits a part of a remaining part of the blue light beam withoutperforming the conversion. Specifically, the fluorescent layer 42 isefficiently excited by the blue light beam having a wavelength of about445 nm, and converts the part of the blue light beam emitted by thelight source device 10 into yellow light (fluorescent light) thatincludes the red light and the green light, and then emits the yellowlight as shown in FIG. 2B. What is denoted with the symbol R in FIG. 2Bis a colored light component available as the red light out of the lightemitted by the fluorescent layer 42. Further, what is denoted with thesymbol G is a colored light component available as the green light outof the light emitted by the fluorescent layer 42. The fluorescent layer42 is formed of a layer including, for example, (Y, Gd)₃(Al, Ga)₅O₁₂:Ceas a YAG fluorescent material.

It should be noted that as the fluorescent layer a layer includinganother fluorescent material for emitting fluorescent including the redlight and the green light can also be used. Further, as the fluorescentlayer, a layer including a mixture of a fluorescent material forconverting the excitation light into the red light and a fluorescentmaterial for converting the excitation light into the green light canalso be used.

As shown in FIG. 1, the collimating optical system 60 is provided with afirst lens 62 for preventing the light beam emitted from the rotatingfluorescent plate 30 from spreading, and a second lens 64 for roughlycollimating the light beam emitted from the first lens 62, andcollectively has a function of roughly collimating the light beamemitted from the rotating fluorescent plate 30. The first lens 62 andthe second lens 64 are each formed of a convex lens.

The first lens array 120 has a plurality of first small lenses 122 fordividing the light beam emitted from the collimating optical system 60into a plurality of partial light beams. The first lens array 120 has afunction of a beam splitting optical element for splitting the lightbeam emitted from the collimating optical system 60 into a plurality ofpartial light beams, and has a configuration of arranging the pluralityof first small lenses 122 in a plane perpendicular to the illuminationlight axis 100 ax in a matrix with a plurality of rows and a pluralityof columns. Although the explanation with reference to a drawing will beomitted, an outer shape of the first small lens 122 is substantiallysimilar to an outer shape of the image forming areas of the liquidcrystal light modulation devices 400R, 400G, and 400B.

The second lens array 130 has a plurality of second small lenses 132corresponding to the plurality of first small lenses 122 of the firstlens array 120. The second lens array 130 has a function of forming theimage of each of the first small lenses 122 of the first lens array 120in the vicinity of the image forming areas of the liquid crystal lightmodulation devices 400R, 400G, and 400B in cooperation with theoverlapping lens 150. The second lens array 130 has a configuration ofarranging the plurality of second small lenses 132 in a planeperpendicular to the illumination light axis 100 ax in a matrix with aplurality of rows and a plurality of columns.

The polarization conversion element 140 is a polarization conversionelement for converting each of the partial beams split into by the firstlens array 120 into a substantially unique linearly polarized light beamhaving a uniform polarization direction, and emitting the resultedpartial light beams.

The polarization conversion element 140 has a polarization split layerfor transmitting one linearly polarized component out of thepolarization components included in the light from the rotatingfluorescent plate 30 without modification while reflecting the otherlinearly polarized component in a direction perpendicular to theillumination light axis 100 ax, a reflecting layer for reflecting theother linearly polarized component, which is reflected by thepolarization split layer, in a direction parallel to the illuminationlight axis 100 ax, and a wave plate for converting the other linearlypolarized component reflected by the reflecting plate into the onelinearly polarized component.

The overlapping lens 150 is an optical element for collecting each ofthe partial light beams from the polarization conversion element 140 tothereby overlap the partial light beams in the vicinity of the imageforming areas of the liquid crystal light modulation devices 400R, 400G,and 400B.

The overlapping lens 150 is disposed so that the optical axis of theoverlapping lens 150 and the light axis of the illumination device 100become substantially identical to each other. It should be noted thatthe overlapping lens 150 can be configured with a compound lens having aplurality of lenses combined with each other. The first lens array 120,the second lens array 130, and the overlapping lens 150 constitute anintegrator optical system for homogenizing the in-plane light intensitydistribution of the light from the rotating fluorescent plate 30.

It should be noted that a rod integrator optical system provided with anintegrator rod can also be used instead of the lens integrator opticalsystem.

The color separation light guide optical system 200 includes dichroicmirrors 210, 220, reflecting mirrors 230, 240, 250, and relay lens 260,270. The color separation light guide optical system 200 has a functionof separating the light beam from the illumination device 100 into thered light beam, the green light beam, and the blue light beam, andrespectively guiding the colored light beams of the red light beam, thegreen light beam, and the blue light beam to the liquid crystal lightmodulation devices 400R, 400G, 400B to be the objects of illumination.

Collecting lenses 300R, 300G, and 300B are disposed between the colorseparation light guide optical system 200 and the liquid crystal lightmodulation devices 400R, 400G, and 400B, respectively.

The dichroic mirrors 210, 220 are mirrors each having a wavelengthselecting transmissive film formed on a substrate, which reflects alight beam in a predetermined wavelength band and transmits a light beamin another wavelength band.

The dichroic mirror 210 is a dichroic mirror for transmitting the redlight component and reflecting the green light component and the bluelight component.

The dichroic mirror 220 is a dichroic mirror for reflecting the greenlight component and transmitting the blue light component.

The reflecting mirror 230 is a reflecting mirror for reflecting the redlight component.

The reflecting mirrors 240, 250 are reflecting mirrors for reflectingthe blue light component.

The red light beam transmitted through the dichroic mirror 210 isreflected by the reflecting mirror 230, and then enters the imageforming area of the liquid crystal light modulation device 400R for thered light beam after being transmitted through the collecting lens 300R.

The green light beam reflected by the dichroic mirror 210 is furtherreflected by the dichroic mirror 220, and then enters the image formingarea of the liquid crystal light modulation device 400G for the greenlight beam after being transmitted through the collecting lens 300G.

The blue light beam having passed through the dichroic mirror 220 entersthe image forming area of the liquid crystal light modulation device400B for the blue light beam via the relay lens 260, the reflectingmirror 240 on the entrance side, the relay lens 270, the reflectingmirror 250 on the exit side, and the collecting lens 300B. The relaylenses 260, 270 and the reflecting mirrors 240, 250 have a function ofguiding the blue light component thus transmitted through the dichroicmirror 220 to the liquid crystal light modulation device 400B.

It should be noted that since the length of the light path of the bluelight beam is larger than the lengths of the light paths of the othercolored light beams, such relay lenses 260, 270 are provided to thelight path of the blue light beam in order for preventing degradation ofthe light efficiency caused by the diffusion of the light beam. In theprojector 1000 according to the first embodiment, such a configurationas described above is adopted because the length of the light path ofthe blue light beam is large. However, it is also possible to adopt theconfiguration in which the length of the light path of the red lightbeam is elongated, and the relay lenses 260, 270 and the reflectingmirrors 240, 250 are used in the light path of the red light beam.

The liquid crystal light modulation devices 400R, 400G, and 400B are formodulating the respective colored light beams having entered inaccordance with the image information to thereby form a color image, andbecome the illumination object of the illumination device 100. It shouldbe noted that, although omitted from the drawings, the entrance sidepolarization plates are disposed between the collecting lenses 300R,300G, 300B and the liquid crystal light modulation devices 400R, 400G,400B, respectively, so as to intervene therebetween, and the exit sidepolarization plates are disposed between the liquid crystal lightmodulation devices 400R, 400G, 400B and the cross dichroic prism 500,respectively, so as to intervene therebetween. The light modulation ofthe respective colored light beam having entered is performed by theentrance side polarization plates, the liquid crystal light modulationdevices 400R, 400G, and 400B, and the exit side polarization platesdescribed above.

The liquid crystal light modulation devices 400R, 400G, and 400B areeach a transmissive liquid crystal light modulation device formed byencapsulating a liquid crystal material as an electro-optic materialbetween a pair of transparent glass plates, and modulates thepolarization direction of one kind of linearly polarized light beamemitted from the entrance side polarization plate in accordance with animage signal provided thereto using, for example, polysilicon TFTs asswitching elements.

The cross dichroic prism 500 is an optical element for combining opticalimages modulated for respective colored light beams emitted from therespective exit side polarization plates to form a color image. Thecross dichroic prism 500 has a substantially rectangular planar shapeformed of four rectangular prisms bonded with each other, and on thesubstantially X-shaped interfaces on which the rectangular prisms arebonded with each other, there are formed dielectric multilayer films.The dielectric multilayer film formed on one of the substantiallyX-shaped interfaces is for reflecting the red light beam, and thedielectric multilayer film formed on the other of the interfaces is forreflecting the blue light beam. The red light beam and the blue lightbeam are deflected by these dielectric multilayer films to have theproceeding direction aligned with the proceeding direction of the greenlight, thus the three colored light beams are combined.

The color image emitted from the cross dichroic prism 500 is projectedin an enlarged manner by the projection optical system 600 to form animage on the screen SCR.

Then, advantages of the illumination device 100 and the projector 1000according to the first embodiment will be explained.

As described above, according to the illumination device 100 related tothe first embodiment, since there are provided the light source device10 for emitting the excitation light (the blue light) and the rotatingfluorescent plate 30 provided with the fluorescent layer 42 forconverting a part or the whole of the excitation light into thefluorescent light that includes two or more colored light beams (the redlight beam and the green light beam), it becomes possible to obtain thea plurality of colored light beams using the light source 10 foremitting the excitation light.

Further, according to the illumination device 100 related to the firstembodiment, since the rotating fluorescent plate 30 provided with asingle fluorescent layer 42 is used, it becomes possible to make themanufacturing process of the rotating fluorescent plate 30 relativelyeasy.

Further, according to the illumination device 100 related to the firstembodiment, since there is used the rotating fluorescent plate havingthe single fluorescent layer 42 formed continuously along thecircumferential direction of the circular disk 40, it results in thatthe same colored light beam is always emitted from the illuminationdevice 100, and as a result, it becomes possible for the illuminationdevice 100 to be applied to the liquid crystal projector of thenon-colorsequential type having no color breakup phenomenon and strongcharacteristics.

Further, according to the illumination device 100 related to the firstembodiment, since there is provided the rotating fluorescent plate 30obtained by providing the single fluorescent layer 42 to the rotatablecircular disk 40, the heat generated in the fluorescent layer 42 due tothe irradiation with the excitation light can be radiated in a largearea along the circumferential direction, and as a result, it becomespossible to prevent the deterioration of the fluorescent layer 42 anddegradation of the luminous efficiency due to overheat of thefluorescent layer 42.

Further, according to the illumination device 100 related to the firstembodiment, since the light source device 10 emits the blue light as theexcitation light, the fluorescent layer 42 converts a part of the bluelight emitted from the light source device 10 into the fluorescent lightbeam that includes the red light and the green light, and at the sametime, transmits a part of a remaining part of the blue light withoutconversion, it becomes possible to emit the white light from theillumination device using the light source device 10 for emitting theblue light.

Further, according to the illumination device 100 related to the firstembodiment, since the circular disk 40 is made of the materialtransmitting the excitation light, the fluorescent layer 42 is formed onthe circular disk 40 via the dichroic film 44 for transmitting theexcitation light and reflecting the fluorescent light, and it isarranged that the excitation light enters the rotating fluorescent plate30 from the side of the circular disk 40, it becomes possible to emitthe illumination light from the illumination device using the so-calledtransmissive rotating fluorescent plate 30.

Further, according to the illumination device 100 related to the firstembodiment, since the light collection optical system 20 is provided, itbecomes possible to emit the fluorescent light in a small area, and as aresult, it becomes possible to improve the light efficiently.

Further, according to the illumination device 100 related to the firstembodiment, since the rotating fluorescent plate 30 rotates at therotational speed at which the focused spot of the excitation light moveson the fluorescent layer 42 at approximately 18 m/sec, it becomespossible to reduce the temperature rise generated in the fluorescentlayer 42 due to the irradiation with the excitation light to anextremely low level, and as a result, it becomes possible to betterprevent the deterioration of the fluorescent layer 42 and thedegradation of the luminous efficiency due to the overheat of thefluorescent layer 42.

Further, according to the illumination device 100 related to the firstembodiment, since the light source device 10 is formed of the lasersource, it becomes possible to project the projection image immediatelyafter the power is on.

Further, according to the illumination device 100 related to the firstembodiment, since the laser source with high light collecting power isused as the light source, it becomes possible to emit the fluorescentlight in a smaller area, and as a result, it becomes possible to betterimprove the light efficiently.

According to the projector 1000 related to the first embodiment, sincethe illumination device 100 is provided, there can be obtained theprojector capable of obtaining a plurality of colored light beams usingthe light source device 10 for emitting the excitation light, capable ofmaking the manufacturing process of the rotating fluorescent plate 30relatively simple, and being realized as a liquid crystal projector.

Further, according to the projector 1000 related to the firstembodiment, since the light source device 10 emits the blue light as theexcitation light, the fluorescent layer 42 converts a part of the bluelight emitted from the light source device 10 into the fluorescent lightbeam that includes the red light and the green light, and at the sametime, transmits a part of a remaining part of the blue light withoutconversion, it becomes possible to project a full-color image using thelight source device 10 for emitting the blue light.

Second Embodiment

FIG. 4 is a top view showing an optical system of a projector 1002according to a second embodiment of the invention.

FIG. 5 is a graph showing the emission characteristics of a second lightsource device 710 in the second embodiment. It should be noted thatsince the emission characteristics of the light source device 10 and thefluorescent layer 46 in the second embodiment are substantially the sameas the emission characteristics of the light source device 10 and thefluorescent layer 42 in the first embodiment, the graphicalrepresentation will be omitted.

The projector 1002 according to the second embodiment basically hassubstantially the same configuration as the configuration of theprojector 1000 according to the first embodiment, but is different fromthe projector 1000 according to the first embodiment in theconfiguration of the illumination device 102, and in the point that asecond illumination device is further provided. Specifically, in theprojector 1002 according to the second embodiment, as shown in FIG. 4,the illumination device 102 emits the light including the red light andthe green light as the illumination light, and the projector 1002 isfurther provided with the second illumination device 700 for emittingthe blue light. Further, in accordance therewith, the structure of thecolor separation light guide optical system is also made different.

Although the illumination device 102 basically has substantially thesame configuration as that of the illumination device 100 according tothe first embodiment, the configuration of the rotating fluorescentplate is different from that of the illumination device 100 according tothe first embodiment. Specifically, in the illumination device 102according to the second embodiment, the fluorescent layer 46 in therotating fluorescent plate 32 converts the blue light emitted from thelight source device 10 into the fluorescent light beam that includes thered light and the green light. More specifically, the fluorescent layer46 is thicker than the fluorescent layer 42 in the first embodiment, andthe blue light having entered the fluorescent layer 46 is converted intothe fluorescent light beam that includes the red light and the greenlight without passing through the fluorescent layer 46.

The second illumination device 700 is provided with a second lightsource device 710, a light collection optical system 720, a scatteringplate 730, a polarization conversion integrator rod 740, and acollecting lens 750.

The second light source device 710 is a laser source for emitting a bluelight beam (having a peak emission intensity at a wavelength of 445 nm,see FIG. 5), which is a laser beam, as a colored light beam. What isdenoted with the symbol B in FIG. 5 is a colored light component emittedby the second light source device 710 as the excitation light beam (theblue light beam).

As shown in FIG. 4, the light collection optical system 720 is providedwith a first lens 722 and a second lens 724. The light collectionoptical system 720 collectively makes the blue light beam enter thescattering plate 730 in a roughly focused state. The first lens 722 andthe second lens 724 are each formed of a convex lens.

The scattering plate 730 scatters the blue light beam emitted from thesecond light source device 710 at a predetermined scattering intensityto thereby obtain the blue light beam having the light distributionsimilar to that of the fluorescent light (the red light and the greenlight emitted from the rotating fluorescent plate 32).

As the scattering plate 730, obscured glass made of optical glass, forexample, can be used.

The polarization conversion integrator rod 740 homogenizes the in-planelight intensity distribution of the blue light from the second lightsource device 710, and converts the polarization direction of the bluelight beam into substantially one kind of linearly polarized light withthe polarization directions aligned. Although the detailed explanationis omitted, the polarization conversion integrator rod has an integratorrod, a reflecting plate disposed on the entrance surface side of theintegrator rod and provided with a small hole through which the bluelight beam enters, and a reflective polarization plate disposed on theside of the exit surface.

It should be noted that a lens integrator optical system together with apolarization conversion element can also be used instead of thepolarization conversion integrator rod.

The collecting lens 750 collects the light from the polarizationconversion integrator rod 740, and then makes the light enter thevicinity of the image forming area of the liquid crystal lightmodulation device 400B.

The color separation light guide optical system 202 is provided with adichroic mirror 210, reflecting mirrors 222, 230, and 250. The colorseparation light guide optical system 202 has a function of separatingthe light beam from the illumination device 102 into the red light beamand the green light beam, and respectively guiding the colored lightbeams of the red light beam and the green light beam from theillumination device 102 and the blue light beam from the secondillumination device 700 to the liquid crystal light modulation devices400R, 400G, 400B to be the illumination objects.

The red light beam transmitted through the dichroic mirror 210 isreflected by the reflecting mirror 230, and then enters the imageforming area of the liquid crystal light modulation device 400R for thered light beam after being transmitted through the collecting lens 300R.

The green light beam reflected by the dichroic mirror 210 is furtherreflected by the reflecting mirror 222, and then enters the imageforming area of the liquid crystal light modulation device 400G for thegreen light beam after passing through the collecting lens 300G.

The blue light beam from the second light source device 700 is reflectedby the reflecting mirror 250, and then enters the image forming area ofthe liquid crystal light modulation device 400B for the blue light beamafter passing through the collecting lens 300B.

As described above, although different from the illumination device 100according to the first embodiment in the configuration of the rotatingfluorescent plate, since the illumination device 102 according to thesecond embodiment is provided with the light source device 10 foremitting the excitation light (the blue light) and the rotatingfluorescent plate 32 provided with the fluorescent layer 46 forconverting a part or the whole of the excitation light into thefluorescent light that includes two or more colored light beams (the redlight beam and the green light beam), it becomes possible to obtain aplurality of colored light beams using the light source 10 for emittingthe excitation light similar to the illumination device 100 according tothe first embodiment.

Further, according to the illumination device 102 related to the secondembodiment, since the rotating fluorescent plate 32 provided with thesingle fluorescent layer 46 is used, it becomes possible to make themanufacturing process of the rotating fluorescent plate 32 relativelyeasy similarly to the illumination device 100 according to the firstembodiment.

Further, according to the illumination device 102 related to the secondembodiment, since there is used the rotating fluorescent plate havingthe single fluorescent layer 42 formed continuously along thecircumferential direction of the circular disk 40, it results in thatthe same colored light beam is always emitted from the illuminationdevice 102, and as a result, it becomes possible for the illuminationdevice 102 to be applied to the liquid crystal projector of thenon-colorsequential type having no color breakup phenomenon and strongcharacteristics similarly to the illumination device 100 according tothe first embodiment.

Further, according to the illumination device 102 related to the secondembodiment, since there is provided the rotating fluorescent plate 32obtained by providing the single fluorescent layer 46 to the rotatablecircular disk 40, the heat generated in the fluorescent layer 46 due tothe irradiation with the excitation light can be radiated in a largearea along the circumferential direction, and as a result, it becomespossible to prevent the deterioration of the fluorescent layer 46 andthe degradation of the luminous efficiency due to the overheat of thefluorescent layer 46 similarly to the illumination device 100 accordingto the first embodiment.

Further, according to the illumination device 102 related to the secondembodiment, since the light source device 10 emits the blue light as theexcitation light, the fluorescent layer 42 converts a part of the bluelight emitted from the light source device 10 into the light includingthe red light and the green light, it becomes possible to emit the lightincluding the red light and the green light from the illumination deviceusing the light source device for emitting the blue light.

It should be noted that the illumination device 102 according to thesecond embodiment has substantially the same configuration as that ofthe illumination device 100 according to the first embodiment in otherpoints than the configuration of the rotating fluorescent plate, andtherefore, obtains the corresponding advantages out of the advantagesthat the illumination device 100 according to the first embodiment has.

Although different from the case of the projector 1000 according to thefirst embodiment in the configuration of the illumination device 102 andin the point that the second illumination device is further provided,according to the projector 1002 related to the second embodiment, sincethe illumination device 102 configured as described above is provided,there can be obtained the projector capable of obtaining a plurality ofcolored light beams using the light source device 10 for emitting theexcitation light, capable of making the manufacturing process of therotating fluorescent plate 32 relatively simple, and being realized as aliquid crystal projector similarly to the case of the projector 1000according to the first embodiment.

Further, according to the projector 1002 related to the secondembodiment, since the light source device 10 emits the blue light, thefluorescent layer 46 converts the blue light emitted from the lightsource device 10 into the fluorescent light that includes the red lightand the green light and then emits the fluorescent light, and theprojector 1002 is provided with the second illumination device 700 foremitting the blue light, it becomes possible to project a full-colorimage using the light source device 10 and the second illuminationdevice 700 for emitting the blue light.

Further, according to the projector 1002 related to the secondembodiment, since the second illumination device 700 is provided withthe second light source device 710 for emitting the blue light and thescattering plate 730 for scattering the light from the second lightsource device 710, it becomes possible to uniform the lightdistributions of the red light and the green light emitted from theillumination device 102 and the light distribution of the blue lightemitted from the second illumination device with each other to therebyproject a more high-quality projection image.

Third Embodiment

FIG. 6 is a top view showing an optical system of a projector 1004according to a third embodiment of the invention.

FIGS. 7A and 7B are diagrams for explaining the rotating fluorescentplate 34 in the third embodiment. FIG. 7A is a front view of therotating fluorescent plate 34, and FIG. 7B is a cross-sectional viewalong the line A2-A2 shown in FIG. 7A.

The illumination device 104 according to the third embodiment basicallyhas a configuration similar to the illumination device 102 according tothe second embodiment, but is different from the illumination device 102according to the second embodiment in the configuration of the rotatingfluorescent plate.

Specifically, in the rotating fluorescent plate 34 in the thirdembodiment, as shown in FIGS. 7A and 7B, the fluorescent layer 46 isformed on the circular disk 40 via a reflecting film 45 for reflectingvisible light (a so-called reflective rotating fluorescent plate), andis configured so as to emit the fluorescent light toward the side whichthe blue light enters from as described later. Further, in accordancewherewith, as shown in FIG. 6, the illumination device 104 according tothe third embodiment is different in the optical position of the lightsource device 10, further provided with a collimating optical system 70,a dichroic mirror 80, and a collimating light collection optical system90, and configured so that the blue light from the light source device10 enters the rotating fluorescent plate 34 from the side of thefluorescent layer 46.

It should be noted that in the case in which the so-called reflectiverotating fluorescent plate is used as described above, there is no needfor using the circular disk made of a material transmitting theexcitation light, but a circular disk made of an opaque material such asmetal can also be used.

The light source device 10 is disposed so as to have an optical axisperpendicular to an illumination light axis 104 ax.

The collimating optical system 70 is provided with a first lens 72 forpreventing the light beam emitted from the light source device 10 fromspreading, and a second lens 74 for roughly collimating the light beamfrom the first lens 72, and collectively has a function of roughlycollimating the light from the light source device 10. The first lens 72and the second lens 74 are each formed of a convex lens.

The dichroic mirror 80 is disposed in the light path from thecollimating optical system 70 to the rotating fluorescent plate 34 (thecollimating light collection optical system 90) so as to intersect eachof the optical axis of the light source device 10 and the illuminationlight axis 104 ax at an angle of 45°. The dichroic mirror 80 reflectsthe blue light, and transmits the red light and the green light.

The collimating light collection optical system 90 has a function ofmaking the blue light from the dichroic mirror 80 enter the fluorescentlayer 46 in a roughly focused state, and a function of roughlycollimating the fluorescent light emitted from the rotating fluorescentplate. The collimating light collection optical system 90 is providedwith a first lens 92 and a second lens 94. The first lens 92 and thesecond lens 94 are each formed of a convex lens.

As described above, although different from the illumination device 102according to the second embodiment in the configuration of the rotatingfluorescent plate, since the illumination device 104 according to thethird embodiment is provided with the light source device 10 foremitting the excitation light (the blue light) and the rotatingfluorescent plate 34 provided with the fluorescent layer 46 forconverting a part or the whole of the excitation light into thefluorescent light including two or more colored light beams (the redlight beam and the green light beam), it becomes possible to obtain aplurality of colored light beams using the light source 10 for emittingthe excitation light similar to the illumination device 102 according tothe second embodiment.

Further, according to the illumination device 104 related to the thirdembodiment, since the rotating fluorescent plate 34 provided with thesingle fluorescent layer 46 is used, it becomes possible to make themanufacturing process of the rotating fluorescent plate 34 relativelyeasy similarly to the illumination device 102 according to the secondembodiment.

Further, according to the illumination device 104 related to the thirdembodiment, since there is used the rotating fluorescent plate havingthe single fluorescent layer 46 formed continuously along thecircumferential direction of the circular disk 40, it results in thatthe same colored light beam is always emitted from the illuminationdevice 104, and as a result, it becomes possible for the illuminationdevice 104 to be applied to the liquid crystal projector of thenon-colorsequential type having no color breakup phenomenon and strongcharacteristics similarly to the illumination device 102 according tothe second embodiment.

Further, according to the illumination device 104 related to the thirdembodiment, since there is provided the rotating fluorescent plate 34obtained by providing the single fluorescent layer 46 to the rotatablecircular disk 40, the heat generated in the fluorescent layer 46 due tothe irradiation with the excitation light can be radiated in a largearea along the circumferential direction, and as a result, it becomespossible to prevent the deterioration of the fluorescent layer 46 andthe degradation of the luminous efficiency due to the overheat of thefluorescent layer 46 similarly to the illumination device 102 accordingto the second embodiment.

Further, according to the illumination device 104 related to the thirdembodiment, since the fluorescent layer 46 is formed on the circulardisk 40 via the reflecting film 45 for reflecting visible light, and itis arranged that the excitation light enters the rotating fluorescentplate 34 from the side of the fluorescent layer 46, it becomes possibleto emit the illumination light from the illumination device using theso-called reflective rotating fluorescent plate 34.

It should be noted that the illumination device 104 according to thethird embodiment has substantially the same configuration as that of theillumination device 102 according to the second embodiment in otherpoints than, for example, the configuration of the rotating fluorescentplate, and therefore, obtains the corresponding advantages out of theadvantages that the illumination device 102 according to the secondembodiment has.

Although different from the case of the projector 1002 according to thesecond embodiment in the configuration of the illumination device 104,according to the projector 1004 related to the third embodiment, sincethe illumination device 104 configured as described above is provided,there can be obtained the projector capable of obtaining a plurality ofcolored light beams using the light source device 10 for emitting theexcitation light, capable of making the manufacturing process of therotating fluorescent plate 34 relatively simple, and being realized as aliquid crystal projector similarly to the case of the projector 1002according to the second embodiment.

It should be noted that the projector 1004 according to the thirdembodiment has substantially the same configuration as that of theprojector 1002 according to the second embodiment in other points thanthe configuration of the illumination device, and therefore, obtains thecorresponding advantages out of the advantages that the projector 1002according to the second embodiment has.

Fourth Embodiment

FIG. 8 is a top view showing an optical system of a projector 1006according to a fourth embodiment of the invention.

The projector 1006 according to the fourth embodiment basically has aconfiguration similar to the projector 1004 according to the thirdembodiment, but is different from the projector 1004 according to thethird embodiment in the configuration of the second illumination device.Specifically, as shown in FIG. 8, in the projector 1006 according to thefourth embodiment, the second illumination device 702 emits the bluelight beam toward the dichroic mirror 80 in an illumination device 106.In the fourth embodiment, the dichroic mirror 80 additionally has afunction of the colored light combination element for merging the lightemitted from the second illumination device 702 into the red light andthe green light emitted from the rotating fluorescent plate 34. Further,in accordance therewith, the configuration of the color separation lightguide optical system is also made different.

The second illumination device 702 is provided with a second lightsource device 710, a light collection optical system 760, a scatteringplate 732, and a collimating optical system 770.

The light collection optical system 760 is provided with a first lens762 and a second lens 764. The light collection optical system 760focuses the blue light from the second light source device 710 in thevicinity of the scattering plate 732. The first lens 762 and the secondlens 764 are each formed of a convex lens.

The scattering plate 732 scatters the blue light beam from the secondlight source device 710 at a predetermined scattering intensity tothereby obtain the blue light beam having the light distribution similarto that of the fluorescent light (the light emitted from the rotatingfluorescent plate 34). As the scattering plate 732, obscured glass madeof optical glass, for example, can be used.

The collimating optical system 770 is provided with a first lens 772 forpreventing the light beam emitted from the second light source device710 from spreading, and a second lens 774 for roughly collimating thelight beam from the first lens 772, and collectively has a function ofroughly collimating the light from the second light source device 710.The first lens 772 and the second lens 774 are each formed of a convexlens.

The color separation light guide optical system 200 in the fourthembodiment has substantially the same configuration as that of the colorseparation light guide optical system 200 in the first embodiment, andtherefore, the explanation therefor will be omitted.

Although different from the case of the projector 1004 according to thethird embodiment in, for example, the configuration of the secondillumination device, according to the projector 1006 related to thefourth embodiment, since the illumination device 106 configured asdescribed above is provided, there can be obtained the projector capableof obtaining a plurality of colored light beams using the light sourcedevice 10 for emitting the excitation light, capable of making themanufacturing process of the rotating fluorescent plate 34 relativelysimple, and being realized as a liquid crystal projector similarly tothe case of the projector 1004 according to the third embodiment.

Further, according to the projector 1006 related to the fourthembodiment, since the dichroic mirror 80 for merging the light emittedfrom the second illumination device 702 into the red light and the greenlight emitted from the rotating fluorescent plate 34 is provided, itbecomes possible to standardize the optical system of the illuminationdevice 106 and the optical system of the second illumination device 702to some extent to thereby make the configuration of the projectorsimpler.

It should be noted that the projector 1006 according to the fourthembodiment has substantially the same configuration as that of theprojector 1004 according to the third embodiment in other points than,for example, the configuration of the second illumination device, andtherefore, obtains the corresponding advantages out of the advantagesthat the projector 1004 according to the third embodiment has.

It should be noted that the illumination device 106 according to thefourth embodiment has substantially the same configuration as that ofthe illumination device 104 according to the third embodiment, andtherefore, obtains the advantages that the illumination device 104according to the third embodiment has.

Fifth Embodiment

FIG. 9 is a top view showing an optical system of a projector 1008according to a fifth embodiment of the invention.

FIGS. 10A through 10D are graphs showing the emission characteristics ofa light source device 12 and a fluorescent layer 48 in the fifthembodiment. FIG. 10A is a graph showing the emission characteristics ofthe light source device 12, FIG. 10B is a graph showing the emissioncharacteristics of a red fluorescent material included in thefluorescent layer 48, FIG. 10C is a graph showing the emissioncharacteristics of a green fluorescent material included in thefluorescent material 48, and FIG. 10D is a graph showing the emissioncharacteristics of the blue fluorescent material included in thefluorescent layer 48.

The projector 1008 according to the fifth embodiment basically has aconfiguration similar to the projector 1004 according to the thirdembodiment, but is different from the projector 1004 according to thethird embodiment in the configuration of the illumination device.Specifically, as shown in FIGS. 9 and 10A through 10D, in the projector1008 according to the fifth embodiment, the illumination device 108 isprovided with a light source device 12 for emitting violet light as theexcitation light, and emits white light as the illumination light. Inaccordance therewith, the projector 1008 according to the fifthembodiment is not provided with the second illumination device, and isdifferent in the configuration of the color separation light guideoptical system.

The light source device 12 is a laser source for emitting a violet lightbeam (having a peak emission intensity at a wavelength of 406 nm, seeFIG. 10A), which is a laser beam, as the excitation light beam. What isdenoted with the symbol V in FIG. 10A is a colored light component (theviolet light beam) emitted by the light source device 12 as theexcitation light beam.

The rotating fluorescent plate 36 basically has substantially the sameconfiguration as that of the rotating fluorescent plate 34 in the thirdembodiment, but is different in the fluorescent layer. The fluorescentlayer 48 in the rotating fluorescent plate 36 is formed of a layerincluding the red fluorescent material for absorbing the violet lightand emitting the red light, the green fluorescent material for absorbingthe violet light and emitting the green light, and the blue fluorescentmaterial for absorbing the violet light and emitting the blue light. Thered fluorescent material is made of, for example, CaAlSiN₃—Si₂N₂O:Eu.The green fluorescent material is made of, for example, Ba₃Si₆O₁₂N₂:Eu.The blue fluorescent material is made of, for example, BaMgAl₁₀O₁₇:Eu.It should be noted that the fluorescent materials are not limited tothose described above, but any other fluorescent materials, which emitthe respective colored light beams in accordance with the excitationlight, can also be adopted.

The fluorescent layer 48 converts the violet light emitted by the lightsource device 12 into the red light, the green light, and the blue lightas the fluorescent light, and then emits the fluorescent light (seeFIGS. 10B through 10D). In FIGS. 10B through 10D, what is denoted withthe symbol R is the colored light component emitted by the redfluorescent material as the red light, what is denoted with the symbol Gis the colored light component emitted by the green fluorescent materialas the green light, and what is denoted with the symbol B is the coloredlight component emitted by the blue fluorescent material as the bluelight.

The color separation light guide optical system 200 in the fifthembodiment has substantially the same configuration as that of the colorseparation light guide optical system 200 in the first embodiment, andtherefore, the explanation therefor will be omitted.

As described above, although different from the case of the illuminationdevice 104 according to the third embodiment in that the light sourcedevice for emitting the violet light is provided and in that the whitelight is emitted as the illumination light, since the illuminationdevice 108 according to the fifth embodiment is provided with the lightsource device 12 for emitting the excitation light (the violet light),and the rotating fluorescent plate 36 provided with the fluorescentlayer 48 for converting a part or the whole of the excitation light intothe fluorescent light that includes two or more colored light beams (thered light and the green light), it becomes possible to obtain aplurality of colored light beams using the light source device 12 foremitting the excitation light similarly to the illumination device 104according to the third embodiment.

Further, according to the illumination device 108 related to the fifthembodiment, since the rotating fluorescent plate 36 provided with thesingle fluorescent layer 48 is used, it becomes possible to make themanufacturing process of the rotating fluorescent plate 36 relativelyeasy similarly to the illumination device 104 according to the thirdembodiment.

Further, according to the illumination device 108 related to the fifthembodiment, since there is used the rotating fluorescent plate havingthe single fluorescent layer 48 formed continuously along thecircumferential direction of the circular disk 40, it results in thatthe same colored light beam is always emitted from the illuminationdevice 108, and as a result, it becomes possible for the illuminationdevice 108 to be applied to the liquid crystal projector of thenon-colorsequential type having no color breakup phenomenon and strongcharacteristics similarly to the illumination device 104 according tothe third embodiment.

Further, according to the illumination device 108 related to the fifthembodiment, since there is provided the rotating fluorescent plate 36obtained by providing the single fluorescent layer 48 to the rotatablecircular disk 40, the heat generated in the fluorescent layer 48 due tothe irradiation with the excitation light can be radiated in a largearea along the circumferential direction, and as a result, it becomespossible to prevent the deterioration of the fluorescent layer 48 andthe degradation of the luminous efficiency due to the overheat of thefluorescent layer 48 similarly to the illumination device 104 accordingto the third embodiment.

Further, according to the illumination device 108 related to the fifthembodiment, since the light source device 12 emits the violet light, andthe fluorescent layer 48 converts the violet light emitted from thelight source device 12 into the fluorescent light that includes the redlight, the green light, and the blue light, and then emits therespective light beams, it becomes possible to emit the white light fromthe illumination device 108 using the light source device 12 foremitting the violet light.

It should be noted that the illumination device 108 according to thefifth embodiment has substantially the same configuration as that of theillumination device 104 according to the third embodiment in otherpoints than the points that the light source device for emitting theviolet light is provided and that the white light is emitted as theillumination light, and therefore, obtains the corresponding advantagesout of the advantages that the illumination device 104 according to thethird embodiment has.

Although different from the case of the projector 1004 according to thethird embodiment in, for example, the configuration of the illuminationdevice, according to the projector 1008 related to the fifth embodiment,since the illumination device 108 is provided, there can be obtained theprojector capable of obtaining a plurality of colored light beams usingthe light source device 12 for emitting the excitation light, capable ofmaking the manufacturing process of the rotating fluorescent plate 36relatively simple, and being realized as a liquid crystal projectorsimilarly to the case of the projector 1004 according to the thirdembodiment.

Further, according to the projector 1008 related to the fifthembodiment, since the light source device 12 emits the violet light, andthe fluorescent layer 48 converts the violet light emitted from thelight source device 108 into the fluorescent light including the redlight, the green light, and the blue light, and then emits therespective light beams, it becomes possible to project a full-colorimage using the light source device 12 for emitting the violet light.

Although the invention is explained hereinabove based on the embodimentsdescribed above, the invention is not limited to the embodimentsdescribed above. The invention can be put into practice in various formswithin the scope and spirit of the invention, and the followingmodifications are also possible, for example.

1. Although in each of the embodiments described above, the rotatingfluorescent plate having the fluorescent layer 42 formed in a part ofthe circular disk 40 is used, the invention is not limited thereto.FIGS. 11A and 11B are diagrams for explaining the rotating fluorescentplate 38 in the modified example. FIG. 11A is a front view of therotating fluorescent plate 38, and FIG. 11B is a cross-sectional viewalong the line A3-A3 shown in FIG. 11A. For example, as shown in FIGS.11A and 11B, it is also possible to use the rotating fluorescent platehaving the fluorescent layer formed on the entire surface of thecircular disk.

2. Although in the first embodiment described above, there are used thelight source device 10 for emitting the blue light and the fluorescentlayer 42 for converting a part of the blue light emitted from the lightsource device 10 into the light including the red light and the greenlight, and transmitting a part of a remaining part of the blue lightwithout performing the conversion, the invention is not limited thereto.For example, it is also possible to use a light source device foremitting violet light or ultraviolet light, and a fluorescent layer forconverting the violet light or the ultraviolet light emitted from thelight source device into the light including the red light, the greenlight, and the blue light.

3. Although in the fifth embodiment there are used the light sourcedevice 12 for emitting the violet light, and the fluorescent layer 48for converting the violet light emitted from the light source device 12into the fluorescent light including the red light, the green light andthe blue light, the invention is not limited thereto. For example, it isalso possible to use a light source device for emitting ultravioletlight, and a fluorescent layer for converting the ultraviolet lightemitted from the light source device into the light including the redlight, the green light and the blue light.

4. Although in each of the embodiments described above, the convexlenses are used as the first lens and the second lens in the collimatingoptical system, the invention is not limited thereto. In essence, issufficient to use the first lens and the second lens with which thecollimating optical system has the function of roughly collimating thelight. Further, the number of lenses constituting the collimatingoptical system can be one, or three or more. The same can be applied tothe collimating light collection optical system in each of the thirdthrough fifth embodiments.

5. Although in each of the embodiments described above, the convexlenses are used as the first lens and the second lens in the lightcollection optical system, the invention is not limited thereto. Inessence, it is sufficient to use the first lens and the second lens withwhich the light collection optical system has the function of roughlyfocusing the light. Further, the number of lenses constituting the lightcollecting optical system can be one, or three or more.

6. Although in each of the third through fifth embodiments describedabove, the rotating fluorescent plate having the fluorescent layerformed on the circular disk via a reflecting film is used, the inventionis not limited thereto. For example, the rotating fluorescent platehaving the fluorescent layer formed directly on the circular disk, whichis made of a material that reflects the visible light, can also be used.

7. Although in each of the second through fifth embodiments describedabove, the second illumination device provided with the scattering plateis used, the invention is not limited thereto. The second illuminationdevice without the scattering plate can also be used.

8. Although in each of the embodiments described above, the light sourcedevice and the second light source device each formed of the lasersource are used, the invention is not limited thereto. For example, itis also possible to use the light source device and the second lightsource device each composed of a light emitting diode or a light sourcelamp for emitting a specific colored light. Further, it is also possibleto use the light source device and the second light source device formedof the respective types of devices different from each other.

9. Although in each of the embodiments described above the explanationis presented showing, as an example, the projector using three liquidcrystal light modulation devices as the liquid crystal light modulationdevice, the invention is not limited thereto. The invention can also beapplied to the projector using one, two, or four or more liquid crystallight modulation devices.

10. Although in each of the embodiments described above the transmissiveprojector is used, the invention is not limited thereto. For example, itis also possible to use a reflective projector. It should be noted herethat “transmissive” denotes that the light modulation device as thelight modulation section is a type of transmitting a light beam such asa transmissive liquid crystal display device, and “reflective” denotesthat the light modulation device as the light modulation section is atype of reflecting a light beam such as a reflective liquid crystaldisplay device. Also in the case in which the invention is applied tothe reflective projector, the same advantages as in the case with thetransmissive projector can be obtained.

11. The invention can be applied to a front projection projector forperforming projection from the side of observing the projected image,and also to a rear projection projector for performing projection fromthe side opposite to the side of observing the projected image.

12. Although in each of the embodiments, the example of applying theillumination device according to the invention to the projector isexplained, the invention is not limited thereto. For example, theillumination device according to the invention can also be applied toother optical equipment (e.g., an optical disk device, a headlight of avehicle, and an illumination device).

The entire disclosure of Japanese Patent Application No. 2010-62090,filed on Mar. 18, 2010 is expressly incorporated by reference herein.

What is claimed is:
 1. An illumination device comprising: a light sourcedevice adapted to emit an excitation light beam; and a rotatingfluorescent plate having a single fluorescent layer formed on a circulardisk, which can be rotated by a motor, continuously along acircumferential direction of the circular disk, the single fluorescentlayer converting a part or whole of the excitation light beam into afluorescent light beam that includes two or more colored light beams andemitting the two or more colored light beams simultaneously.
 2. Theillumination device according to claim 1, wherein the light sourcedevice emits a blue light beam as the excitation light beam, and thefluorescent layer converts a part of the blue light beam emitted fromthe light source device into the fluorescent light beam that includes ared light beam and a green light beam, and transmits a part of aremaining part of the blue light beam without performing the conversion.3. A projector comprising: the illumination device according to claim 2;a light modulation device adapted to modulate an illumination light beamemitted from the illumination device in accordance with imageinformation; and a projection optical system adapted to project amodulated light emitted from the light modulation device as a projectionimage.
 4. The illumination device according to claim 1, wherein thelight source device emits one of a violet light beam and an ultravioletlight beam as the excitation light beam, and the fluorescent layerconverts the one of the violet light beam and the ultraviolet light beamemitted from the light source device into the fluorescent light beamthat includes a red light beam, a green light beam and a blue lightbeam.
 5. A projector comprising: the illumination device according toclaim 4; a light modulation device adapted to modulate an illuminationlight beam emitted from the illumination device in accordance with imageinformation; and a projection optical system adapted to project amodulated light emitted from the light modulation device as a projectionimage.
 6. The illumination device according to claim 1, wherein thelight source device emits a blue light beam as the excitation lightbeam, and the fluorescent layer converts the blue light beam emittedfrom the light source device into the fluorescent light beam thatincludes a red light beam and a green light beam.
 7. A projectorcomprising: the illumination device according to claim 6; a secondillumination device adapted to emit a blue light beam; a lightmodulation device adapted to modulate an illumination light beam emittedfrom the illumination device in accordance with image information; and aprojection optical system adapted to project a modulated light emittedfrom the light modulation device as a projection image.
 8. The projectoraccording to claim 7, further comprising: a colored light beam combiningelement adapted to combine the blue light beam emitted from the secondillumination device and the red light beam and the green light beamemitted from the rotating fluorescent plate with each other.
 9. Theprojector according to claim 7, wherein the second illumination deviceincludes a second light source device adapted to emit the blue lightbeam, and a scattering plate adapted to scatter the light beam emittedfrom the second light source device at a predetermined scatteringintensity.
 10. The illumination device according to claim 1, wherein thecircular disk is made of a material transmitting the excitation lightbeam, the fluorescent layer is formed on the circular disk via adichroic film adapted to transmit the excitation light beam and toreflect the fluorescent light beam, and the excitation light beam isarranged to enter the rotating fluorescent plate from a side of thecircular disk.
 11. A projector comprising: the illumination deviceaccording to claim 10; a light modulation device adapted to modulate anillumination light beam emitted from the illumination device inaccordance with image information; and a projection optical systemadapted to project a modulated light emitted from the light modulationdevice as a projection image.
 12. The illumination device according toclaim 1, wherein the fluorescent layer is formed on the circular diskvia a reflecting film adapted to reflect a visible light beam, and theexcitation light beam is arranged to enter the rotating fluorescentplate from a side of the fluorescent layer.
 13. A projector comprising:the illumination device according to claim 12; a light modulation deviceadapted to modulate an illumination light beam emitted from theillumination device in accordance with image information; and aprojection optical system adapted to project a modulated light emittedfrom the light modulation device as a projection image.
 14. Theillumination device according to claim 1, further comprising: a lightcollection optical system disposed in a light path from the light sourcedevice to the rotating fluorescent plate, and adapted to make theexcitation light beam enter the fluorescent layer in a roughly focusedstate.
 15. A projector comprising: the illumination device according toclaim 14; a light modulation device adapted to modulate an illuminationlight beam emitted from the illumination device in accordance with imageinformation; and a projection optical system adapted to project amodulated light emitted from the light modulation device as a projectionimage.
 16. The illumination device according to claim 1, wherein therotating fluorescent plate rotates at a rotational speed at which afocused spot of the excitation light beam moves on the fluorescent layerat a predetermined relative speed in a range of 5 msec through 50 msec.17. A projector comprising: the illumination device according to claim16; a light modulation device adapted to modulate an illumination lightbeam emitted from the illumination device in accordance with imageinformation; and a projection optical system adapted to project amodulated light emitted from the light modulation device as a projectionimage.
 18. The illumination device according to claim 1, wherein thelight source device is formed of a laser source.
 19. A projectorcomprising: the illumination device according to claim 1; a lightmodulation device adapted to modulate an illumination light beam emittedfrom the illumination device in accordance with image information; and aprojection optical system adapted to project a modulated light emittedfrom the light modulation device as a projection image.
 20. Anillumination device according to claim 1 comprising: a light sourcedevice adapted to emit an excitation light beam; and a rotatingfluorescent plate having a single fluorescent layer formed on a circulardisk, which can be rotated by a motor, continuously along acircumferential direction of the circular disk, an entirety of thesingle fluorescent layer adapted to convert a part or whole of theexcitation light beam into a fluorescent light beam that includes two ormore colored light beams.